So I am implementing a custom navigation item in my view controller via the method like this
-(UINavigationItem*)navigationItem{
item = [[SearchNavigationItem alloc] init];
item.delegate = self;
return item;
}
The SearchNavigationItem will set itself up, add a UITextField and so on.
The field.delegate will have the item as the delegate.
So the issue I have is that when I try to grab the text of the field, it is nil. But when the "textfield changed" is called, I can access the field via the argument (textFieldDidChange:UITextField*) and it has the text.
Another issue, like the title, was that when I did [field resignFirstResponder] nothing happened.
Okay so I already have the answer, and I am writing this question because I could personally not find any help while fixing it.
So the issue is that navigationItem can be called multiple times and this kept creating new bars.
So the solution became, simply, this:
-(UINavigationItem*)navigationItem{
// Apparently it should be treated as a 'singleton' which I think it says
// kind of in the documentation. This comment is just to reinforce that
// it burned me to init it each time this method is called. Which is can
// be multiple times and also outside of the class itself (like when nav'ing)
if(item == nil){
item = [[SearchNavigationItem alloc] init];
item.delegate = self;
}
return item;
}
Hope this helps someone else.
Related
Beginner programmer trying to understand why I cannot accomplish this simple task. I know it is most likely a very simple solution but hoping that someone will explain the WHY.
I have a screen where users can input emails into a textfield. The idea is that if upon entering the e-mail, if it is not already in the stored emails, it will prompt the user to enter the new email/contact into the store. Since I check if the e-mail is valid BEFORE popping up the screen for contact creation, I'd like to take the text entered and put it directly into the "Email" field on the new contact creation page and not allow editing. I've tried numerous methods but CANNOT get the email to show up in the text field. Can someone explain why this is?
Code from initial VC where users enter their emails. If the email does not exist in the store, this code creating the contact creator page is fired:
//I created this custom initializer since setting the text field (as I did below) would not work
ContactCreationViewController *contactCreationVC = [[ContactCreationViewController alloc] initWithEmail:trimmedText];
contactCreationVC.delegate = self;
//initially I tried setting the text here but it did not work, I now understand why
//[contactCreationVC.emailField setText:#"asdsadasd"];
[contactCreationVC setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[contactCreationVC setModalPresentationStyle:UIModalPresentationOverCurrentContext];
[self presentViewController:contactCreationVC animated:YES completion:nil];
This is the code for the actual ContactCreatorVC:
-(instancetype) initWithEmail:(NSString*)email{
self = [super init];
//tried setting email here which works as I check with breakpoints
[self setEmail:email];
//self.email = email here when I check
return self;
}
....
- (nonnull UITableViewCell *)tableView:(nonnull UITableView *)tableView cellForRowAtIndexPath:(nonnull NSIndexPath *)indexPath {
switch (indexPath.row) {
....
case 3: {
ContactCreationTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:contactCreationCellIdentifier];
cell.titleLabel.text = #"E-Mail";
cell.userEntryTextfield.tag = 3;
cell.userEntryTextfield.delegate = self;
cell.userEntryTextfield.keyboardType = UIKeyboardTypeEmailAddress;
//I try setting the email here but self.email = nil (don't understand why)
cell.userEntryTextfield.text = [NSString stringWithFormat:#"%#", self.email];
cell.userEntryTextfield.userInteractionEnabled = NO;
cell.userEntryTextfield.autocapitalizationType = UITextAutocapitalizationTypeNone;
self.emailField = cell.userEntryTextfield;
return cell;
}
.....
}
I feel stupid for even asking such a simple question but I clearly am not understanding what is going on behind the scenes cause I've tried everything. Can anyone explain what is going on and suggest the ideal solution from a best practice standpoint?
EDIT: I guess my question could be more concise...it basically boils down to: why when I set self.email in the init does it not stick when I access self.email in the cellForRow method (it becomes nil)?
(the textfield is in a cell in a tableview)
The problem is this line:
[contactCreationVC.emailField setText:#"asdsadasd"];
You have only just created contactCreationVC. Its view has not loaded, so emailField is nil (easily demonstrated by some rudimentary logging). A message to nil does nothing.
The correct approach is: never touch another view controller's outlets. Set a property of the other view controller and let it deal with its own outlets. In this case, the other view controller would need to use the property to set the emailField text in its viewDidLoad.
As to why that approach doesn't work for you, there isn't enough info to answer it as far as I can tell. If you can prove that things go in this order:
A ContactCreatorVC init is called with an actual email value, and the property is set.
The property has a strong (retain) policy so the value is retained.
The very same ContactCreatorVC instance now has its cellForRowAtIndexPath called, and that moment the property is nil.
If you can prove all that, then the only logical conclusion is that meanwhile some other code has come along and set the property to nil.
I'm working on a project that has many view controllers. Suppose that they are:
A -> B -> C -> D -> E ->F ->G -> H. Each of them has a back and a next button to switch to another view and has many text fields.
I typed text into every textfield. From H view, I can go back to previous views by popviewcontroller and review typed data. but when I click on next button again, all of data on the view were lost. I need to back/next continuous without losing data. How can I do that?
Create a Singleton class.
Give in Singleton class a property like Form *form;
If you start your first ViewController create a new Form
[Singleton sharedInstance].form = [[Form alloc] init];
On leave first ViewController set property from TextField
[Singleton sharedInstance].form.name = textField.text
On leave second ViewController set property
[Singleton sharedInstance].form.mail = textField.text
In each ViewController in viewWillAppear method set stored text
self.textField.text = [Singleton sharedInstance].form.name
or
self.textField.text = [Singleton sharedInstance].form.mail
It's a simple example, but hope it helps to understand what is to do :)
What about using a NSMutableDictionary to keep the models for each view controller as a key value pair. And Each View Controller initialized with this NSMutableDictionary
- (id) initWithDataDictionary:(NSMutableDictionary *)aDataDictionary
{
self = [super init];
_myDataModel = (MyDataModel*)[aDictionary valueForKey:#"MyKeyName"];
if(_myDataModel == nil)
{
_myDataModel = [MyDataModel alloc] init];
aDataDictionary setValue:_myDataModel forKey:#"MyKeyName"];
}
return self;
}
- (void) viewDidLoad
{
[super viewDidLoad];
[self displayData];
}
- (void) displayData
{
self.text1.text = _myDataModel.name;
}
You may also able to keep a key-value pair for setting focus to a last focused textfield.
I see two options here:
If you use storyboards unwind segues are very good option.
Else you can create own delegate.
I am trying to implement a feature in iOS project that when you select a piece of text and highlight it you can then choose from the menu options to use another app like the default dictionary. Is it possible to do this? If so where can I find such documentation or tutorials?
You are describing the iOS menu. Look at the documentation on classes such as UIMenu, UIMenuItem, and UIMenuController.
I've found a solution to my problem.
Thanks to the author of this article:
http://blog.studiovillegas.com/2014/02/06/ios-uipasteboard-uimenucontroller-and-uimenuitem/
To add a custom menu item on to the default menu controller.
ViewController.h
- (void)longPressGestureRecognizer:(UIGestureRecognizer *)recognizer
{
UIMenuItem *mi = [self.label menuItemOpenPleco];
UIMenuController *menuController = [UIMenuController sharedMenuController];
menuController.menuItems = #[mi];
}
PasteboardLabel {h,m}
#interface PasteboardLabel : UILabel
- (UIMenuItem *)menuItemOpenPleco;
#end
#implementation PasteboardLabel
- (UIMenuItem *)menuItemOpenPleco
{
return [[UIMenuItem alloc] initWithTitle:#"Open Pleco" action:#selector(openPleco:)];
}
- (void)openPleco:(id)sender
{
NSString *selectedText = [self textInRange:[self selectedTextRange]];
UIPasteboard *pb = [UIPasteboard generalPasteboard];
pb.string = selectedText;
NSString *urlString = [NSString stringWithFormat:#"plecoapi://x-callback-url/q?s=%#", pb.string];
NSURL *url = [[NSURL alloc] initWithString:urlString];
[[UIApplication sharedApplication] openURL:url];
}
#end
I've found that there's a dearth of examples of adding custom menu items, or explanations of how they work. So I wanted to resolve that by sharing a few important tidbits then showing an example.
The UIMenuController "talks" with UIViews, not with UIViewControllers. This means that your UIMenuController related code needs to go into subclasses of UIView rather than a UIViewController.
Notice the word The at the start of my prior example. There's only one UIMenuController, a singleton which is shared from when your application first starts until it ends. This means that you should only add your item once, and that you shouldn't be writing over the existing array of items.
The appearance of the button in the UIMenu is based on whether or not the UIView that was tapped responds to the selector. This means you need to implement the method if you want the button to appear, and that you don't need to worry about it appearing when unrelated views are tapped unless you pick a selector name for which other UIViews also have methods.
So, having said all that, I made a subclass of a UITextView (which means its a subclass of UIView per my first bullet) and then I gave it this initialize method, along with an implementation for my selector.
+ (void)initialize {
static dispatch_once_t addInsert;
dispatch_once(&addInsert, ^{
UIMenuController *mController = [UIMenuController sharedMenuController];
UIMenuItem *insert = [[UIMenuItem alloc] initWithTitle:#"Insert..."
action:#selector(insert:)];
mController.menuItems = [mController.menuItems arrayByAddingObject:insert];
});
}
- (void)insert:(id)sender {
NSLog(#"Insert... pressed!");
}
The important points above here:
It's in the class initialize method, which is called by the runtime before the first time any other method in your class is invoked. In practice means the code is handled just before the first time an instance of your custom view will be appearing on screen.
I added a dispatch_once guard around it. If my class is subclassed, it's possible that those subclasses will call this initialize method. Maybe those subclasses show up before this one does, so I don't want to prevent the initialize method from running then. I just want to prevent it from running multiple times. Thus why I wrapped the code in a dispatch_once.
I didn't just set the menuItems to a new array of items - I assigned it to a new array of items that extended the existing array of items with my new item.
Hope you find all of that helpful. It's not very complicated, and you can certainly go about implementing my second point in other ways - I tried to pick a way that seemed safest to me, but there are certainly simpler ways of doing it.
I created a Master-Detail-Application, which uses one DetailViewController and multiple TableViewDataSources. Every time the user touches an item, i check the items class and choose the right TableSource for it.
Just like this:
if ([_detailItem isKindOfClass: [cAdress class]]) {
self.dataSource = [[AddressDetailTableSource alloc] init];
((AddressDetailTableSource *) dataSource).current = _detailItem;
} else if ([_detailItem isKindOfClass: [cActivities class]]) {
self.dataSource = [[ActivityDetailTableSource alloc] init];
((ActivityDetailTableSource *) dataSource).current = _detailItem;
}...
Sometimes i go more into Detail and push a new DetailView above the current DetailView. I do this a lot with some different views. Choosing an item in the MasterView causes, that the application goes back to the first DetailView (popToRootViewController).
I now have a problem with one view in particular. When this view is on Top and i choose an item in the MasterView, my App crashes. With NSZombies i found out, that it still tries to build the table with the wrong DataSource. Or at least it tries to call "titleForHeaderInSection" on the wrong DataSource. The error message is:
[ItemDetailTableSource tableView:titleForHeaderInSection:]:message sent to deallocated instance...
The error only occurs with this specific TableSource, also i treat same all the same.
Can anyone help me to get rid of this problem?
Any help is appreciated!
I think your app is trying to access datasource using deallocated instance, you better have individual classes for each tableView, it will simplify your work, always try to modulize the classes instead of trying to put everything in just one class.
I just witnessed a very strange issue where my view would ignore all of the delegate calls coming from a custom view because I called alloc/init on the item at the load. I'm curious as to why.
#synthesize customTextField;
-(void)viewDidLoad {
// by calling this alloc/init, none of the changes here actually update to the view
// everything is ignored from here on in.
// if I comment out the alloc/init line, everything works fine
self.customTextField = [[UITextField alloc] init];
self.customTextField.text = #"Some text";
// setting font and size as well
}
While I would still get calls to the text field delegate methods, none were linked to my specific text fields. I could not respond to just customTextField.
I do realize that calling alloc/init will give me a completely new instance of customTextField... but why wouldn't that new instance be linked to IB and my view?
Because IB linking != binding.
When you link a variable in IB, it's a simply sets the variable once on first load, that's it. It does no other special code to track any changes to it, for good reason.
For example:
You are designing a UITableViewCell, and if you have a cell that is selected, you must rearrange all of the content inside the cell. In this case, you determined it would be easier if you just recreated all of the subviews and re-added them into the view, so you do the following:
-(void) layoutSubviews {
if (cellIsSelected)
{
// custom button is an IBOutlet property, which is by default a subview of self
self.customButton = [UIButton buttonWithType:UIButtonTypeCustom];
[[self someSubView] addSubview:customButton];
}
else {
// where is customButton located now? is it a subview of self or `someSubView`?
self.customButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
// [self addSubview:customButton];
}
}
Thus, it is much easier for IB to say let's set this once, and let the programmer figure the rest out than for IB to try and track all changes made to an object and report them the to the UI.
viewDidLoad is called after your nib is loaded, and creating a new UITextField instance at this point will not be associated with your nib. If you're setting up new instances manually you also need to manually setup the delegates, and add them as subviews of your view.
The XIB file has no way of knowing that you are changing the reference. Consider the following piece of code
NSObject *myObjA = [[NSObject alloc]init]; //create object
NSObject *myObjB = myObjA; //assign reference <- this is the your case after xib load
myObjB = [[NSObject alloc]init]; //create object, myObjA still lives on.
It's basically the same that happens when you load your XIB file; You get the reference to the instantiated object (equals myObjB in above example). You can do with the reference what ever you please but you do not change the interface instance just by creating a new object.